1. Field of the Invention
This invention relates to an apparatus which utilizes heated fluid for controllably thermally ablating tissue in a body cavity and more particularly relates to an apparatus for performing thermal ablation of the endometrium of a uterus by use of an insulated catheter having a thermally conductive inflatable means.
2. Description of the Prior Art
It is well known in the art to use heated fluid for treatment of the human body. One such known device is a hot water bottle which is used to apply heat locally to a selected portion of the body. The temperature of the heated fluid is typically maintained at a level that does not burn the body or thermally damage the tissue.
It is also know in the art to utilize what is referred to as the "Elliot Treatment" machine or the "Elliot treatment regulator" to thermally treat selected regions of the body. The "Elliot treatment regulator" has thin rubber applicators which are adapted to have heated water circulated therethrough under pressure. In use, the thin rubber applicators are placed into contact with selected regions of the body. The temperature and pressure of the water passed through the thin rubber applicators can be controlled accurately. Rubber applicators having various sizes and shapes have been fabricated for numerous applications. Specifically, rubber applicators have been fabricated for vaginal and rectal applications, e.g. for direct application of heat to the large intestine.
In the known vaginal application using the above described device, a vaginal applicator was fabricated to fit into the fornices of the vagina. When the vagina applicator was distended by pressure, the applicator functioned to apply heat directly to and "iron out" the vaginal rugae and came in contact with a layer portion of the mucosa. The above application used conductive heat because it was the most superficial and because there was less penetration.
An excellent summary of known prior art devices for heat treatment, including those briefly described above, and a description of the other related effects thereof such as: (1) physiologic effects of local heating; (2) technic of local application of heat; (3) indications for the employment of local heating; (4) contraindications to and dangers and limitations of local application of heat; and (5) conclusions with regard to local applications of conductive heat are set forth in a Reference Book entitled PHYSICAL MEDICINE published by W. B. Saunders, 1941, written by F. Krusem, M.D., at pages 156 through 165 (the "Physical Medicine Reference") The Physical Medicine Reference at pages 158, 159 sets forth the following summary concerning temperatures relating to use of heat for treatment of the human body:
"The physiologic basis for the employment of heat has been well reviewed by Bazett. In spite of the fact that it is generally considered that a temperature of 98.6.degree. F. (37.degree. C.) exists throughout the normal human body, actually the temperature of the blood in peripheral regions is fare below the central temperature. Temperatures of skin, fat and muscle in peripheral regions are variable and considerably lower than the rectal temperature. Local applications of heat will tend to bring the temperature in peripheral regions to higher levels. Bazett calculated the temperature limit beyond which tissues are damaged, at least by loca hot baths, at approximately 113.degree. F. (45.degree. C.). If baths of this temperature are employed for an hour or more, edema may be noted which will last for twelve to twenty-four hours. Most observers believe that dry hot air temperatures of much higher degrees can be tolerated, however, The vaginal mucosa will tolerate considerably higher temperatures of conductive heat than will the skin; the former apparently is able to withstand temperatures of 116.degree. F. (46.6.degree. C.) for many hours and temperatures of 125.degree. F. (51.7.degree. C.) for short periods of time up to one hour. Variations in the temperature of the skin, subcutaneous tissues and superficial muscle fibers may exceed 36.degree. F. (20.degree. C.) for short periods of time without such changes being necessarily injurious. PA0 When heat is applied locally, blood vessels become dilated and the rate of the flow of blood is increased. The increase in the rapidity of circulation intensifies the thermal conductivity of the tissues and tends to distribute the heat throughout the body, thus hindering the rise in local temperature. Local applications of heat, therefore, always tend to produce a generalized increase of temperature. On exposure to heat, transference of fluid from the blood to the tissues will be increased. When the blood is warmed, the acidity and the carbon dioxide tension are increased. It has been suggested that the changes in tension of cabon dioxide, and possibly also those in acidity, may be of some value in modifying the reactions of tissues to infections. There is evidence that local applications of heat increase phagocytic and local metabolic activity."
It is know in the art to use other techniques and/or apparatus for endometrical ablation of the uterus. One known method utilizes a YAG Laser through an endoscope to destroy tissue of the endometrium to coagulate blood stopping bleeding, to resect fibroids and the like. Also, it is known in the art to use electrosurgical techniques to obtain substantially equivalent results as that of the YAG Laser wherein a radio frequency electrosurgical current is applied through a roller ball electrode of a resectoscope to the endometerium performing endometrial ablation.